1 files changed, 26 insertions, 0 deletions
diff --git a/scripts/argparse_actions.py b/scripts/argparse_actions.py
new file mode 100644
index 0000000..d1d1bfd
--- /dev/null
+++ b/scripts/argparse_actions.py
@@ -0,0 +1,26 @@
+"Custom actions for argparse"
+from pathlib import Path
+from typing import Any, Union, Sequence, Optional
+from argparse import Action, Namespace, ArgumentError, ArgumentParser
+
+class FileCheck(Action):
+    "Action class to check existence of a given file path."
+
+    def __init__(self, option_strings, dest, **kwargs):
+        "Initialise the FileCheck action class"
+        super().__init__(option_strings, dest, **kwargs)
+
+    def __call__(# pylint: disable=[signature-differs]
+            self, parser: ArgumentParser, namespace: Namespace,
+            values: Union[str, Sequence[Any], None],
+            option_string: Optional[str] = "") -> None:
+        """Check existence of a given file path and set it, or raise an
+        exception."""
+        the_path = str(values or "")
+        the_file = Path(the_path)
+        if not the_file.is_file():
+            raise ArgumentError(
+                self,
+                f"The file '{values}' does not exist or is a folder/directory.")
+
+        setattr(namespace, self.dest, values)